The present invention relates to a pinch clamp assembly for engaging a tube with an enteral feeding pump adapted to feed nutritionals or an infusion pump adapted or to infuse medical solutions to a patient. More particularly, the present invention relates to a pinch clamp assembly in the form of a cassette with a clamping element for use on enteral feeding sets or infusion sets and the like, wherein the clamping element prevents the free-flow of enteral formula through the enteral feeding set or of solutions through the infusion set unless the cassette and the clamping element are properly mounted in a housing or some other structure of an enteral feeding pump or infusion pump.
The use of infusion and feeding sets to administer solutions and food to a patient is well known in medical arts. Infusion and enteral sets are used for both enteral and parenteral application, respectively. For hygienic reasons the infusion and enteral sets must be disposed of immediately after use, making it single-use equipment which may be recycled afterwards. Enteral feeding pumps are used to provide the patient with nutrition and medication (formula) when they are unable, for a variety of reason, to eat normally. Parenteral (intravenous) solutions are provided to patients to ensure adequate hydration and to provide needed nutrients, minerals and medication. Often, the enteral or infusion set is placed in a free standing arrangement in which gravity forces the formula or solution into the patient. The rate at which the solution enters the patient can be roughly controlled by various clamps, such as roller clamps, which are currently available on the market.
In many applications, it is necessary to precisely control the amount of solution or formula which enters the patient. When this is the case, a regulating device such as an infusion pump, is placed along the infusion set to control the rate at which the solution is fed to the patient. In application where a pump etc. is used the clamps used to regulate flow are typically open to their fullest extent to prevent the clamp from interfering with the proper functioning of the pump. The clamp is opened with the expectation that the enteral feeding pump or infusion will control fluid flow through the enteral or infusion set. However, emergencies or other distractions may prevent the medical personnel from properly loading the enteral or infusion sets in the enteral feeding pump or the infusion pump. Furthermore, the enteral or infusion sets may be inadvertently dislodged from the pump during operation of the pump.
When the enteral or infusion set is not properly loaded in the pump and the clamp has been opened, a situation known as free-flow often develops. The force of gravity causes the solution or the formula to flow freely into the patient unchecked by the pump or other regulating device. Under a free-flow condition, an amount of solution or formula many times the desired dose can be supplied to the patient within a relatively short time period. This can be particularly dangerous if the solution contains potent medicine or the patient's body is not physically strong enough to adjust to the large inflow of solution or formula. Thus there is a need for a device that prevents a free-flow condition if the enteral or infusion set is not properly mounted in the pump or other regulation means. It is furthermore important that the device is tamper-resistant with regard to the generation of the free-flow condition. Another requirement for such enteral feeding or infusion sets is a long storage period which may be up to several years. Therefore a sticking and continuous deformation of the silicon tube is to be avoided which may result in a deviation of its regular flow properties when using it.
Several approaches have been taken to avoid the above mentioned free-flow situation one of which is disclosed in WO 96/030679 A1. Therein, a pinch clip occluder utilizes a clamping mechanism with at least one arm nested at least partially within a housing which serves as an adjustment mechanism by moving the arm between a position in which the arm occludes flow through an infusion set, and a position in which it allows free-flow through the infusion set. One problem related therewith is that the pinch clip occluder can still be manipulated in a way that the spring force may be countered by other external elements such as a squeeze, a fastener or the like. Furthermore, the metal spring inside the pinch clip occluder according to WO 96/030679 A1 is not made of plastic material thus preventing the possibility of being recycled together with the other plastic components. This makes the recycling process of the infusion set more tedious and thus more expensive. Another disadvantage of said infusion set including the pinch clip occluder is that mounting it to the infusion or enteral feeding pump is rather complicated, i.e. the silicon tube has to be positioned exactly in the recesses formed therefore and wrapped around the rotor unit etc. In addition, a major drawback of this known pinch clip occluder is that when the cap with the prone is left inside the pinch clip occluder to open the tube, a free-flow situation is caused even when the infusion set is not attached to the pump. U.S. Pat. No. 4,689,043 describes an IV tube activator for use with a peristaltic IV infusion pump comprising means that require the closure of a tube associated clamp upon engagement of the IV tube with the pump and upon any subsequent disengagement of the IV tube from the pump. This IV tube activator also represents a rather complicated structure and will not solve the problem of storage of the clamped silicon tube before using it in the infusion pump. Furthermore, setting up the infusion set with the IV tube activator is cumbersome and error-prone due to the many different components.